diff --git a/src/server/editorServices.ts b/src/server/editorServices.ts
index 1fc71711ea..30a9844eaf 100644
--- a/src/server/editorServices.ts
+++ b/src/server/editorServices.ts
@@ -486,7 +486,7 @@ namespace ts.server {
 
         private readonly hostConfiguration: HostConfiguration;
         private safelist: SafeList = defaultTypeSafeList;
-        private legacySafelist: { [key: string]: string } = {};
+        private readonly legacySafelist = createMap<string>();
 
         private pendingProjectUpdates = createMap<Project>();
         /* @internal */
@@ -638,14 +638,14 @@ namespace ts.server {
                 this.safelist = raw.typesMap;
                 for (const key in raw.simpleMap) {
                     if (raw.simpleMap.hasOwnProperty(key)) {
-                        this.legacySafelist[key] = raw.simpleMap[key].toLowerCase();
+                        this.legacySafelist.set(key, raw.simpleMap[key].toLowerCase());
                     }
                 }
             }
             catch (e) {
                 this.logger.info(`Error loading types map: ${e}`);
                 this.safelist = defaultTypeSafeList;
-                this.legacySafelist = {};
+                this.legacySafelist.clear();
             }
         }
 
@@ -2721,13 +2721,13 @@ namespace ts.server {
                         if (fileExtensionIs(baseName, "js")) {
                             const inferredTypingName = removeFileExtension(baseName);
                             const cleanedTypingName = removeMinAndVersionNumbers(inferredTypingName);
-                            if (this.legacySafelist[cleanedTypingName]) {
+                            const typeName = this.legacySafelist.get(cleanedTypingName);
+                            if (typeName !== undefined) {
                                 this.logger.info(`Excluded '${normalizedNames[i]}' because it matched ${cleanedTypingName} from the legacy safelist`);
                                 excludedFiles.push(normalizedNames[i]);
                                 // *exclude* it from the project...
                                 exclude = true;
                                 // ... but *include* it in the list of types to acquire
-                                const typeName = this.legacySafelist[cleanedTypingName];
                                 // Same best-effort dedupe as above
                                 if (typeAcqInclude.indexOf(typeName) < 0) {
                                     typeAcqInclude.push(typeName);
diff --git a/src/testRunner/unittests/tsserverProjectSystem.ts b/src/testRunner/unittests/tsserverProjectSystem.ts
index 2105ce6ef4..9c4d776d54 100644
--- a/src/testRunner/unittests/tsserverProjectSystem.ts
+++ b/src/testRunner/unittests/tsserverProjectSystem.ts
@@ -1826,6 +1826,63 @@ namespace ts.projectSystem {
             }
         });
 
+        it("file with name constructor.js doesnt cause issue with typeAcquisition when safe type list", () => {
+            const file1 = {
+                path: "/a/b/f1.js",
+                content: `export let x = 5; import { s } from "s"`
+            };
+            const constructorFile = {
+                path: "/a/b/constructor.js",
+                content: "const x = 10;"
+            };
+            const bliss = {
+                path: "/a/b/bliss.js",
+                content: "export function is() { return true; }"
+            };
+            const host = createServerHost([file1, libFile, constructorFile, bliss, customTypesMap]);
+            let request: string | undefined;
+            const cachePath = "/a/data";
+            const typingsInstaller: server.ITypingsInstaller = {
+                isKnownTypesPackageName: returnFalse,
+                installPackage: notImplemented,
+                inspectValue: notImplemented,
+                enqueueInstallTypingsRequest: (proj, typeAcquisition, unresolvedImports) => {
+                    assert.isUndefined(request);
+                    request = JSON.stringify(server.createInstallTypingsRequest(proj, typeAcquisition, unresolvedImports || server.emptyArray, cachePath));
+                },
+                attach: noop,
+                onProjectClosed: noop,
+                globalTypingsCacheLocation: cachePath
+            };
+
+            const projectName = "project";
+            const projectService = createProjectService(host, { typingsInstaller });
+            projectService.openExternalProject({ projectFileName: projectName, options: {}, rootFiles: toExternalFiles([file1.path, constructorFile.path, bliss.path]) });
+            assert.equal(request, JSON.stringify({
+                projectName,
+                fileNames: [libFile.path, file1.path, constructorFile.path, bliss.path],
+                compilerOptions: { allowNonTsExtensions: true, noEmitForJsFiles: true },
+                typeAcquisition: { include: ["blissfuljs"], exclude: [], enable: true },
+                unresolvedImports: ["s"],
+                projectRootPath: "/",
+                cachePath,
+                kind: "discover"
+            }));
+            const response = JSON.parse(request!);
+            request = undefined;
+            projectService.updateTypingsForProject({
+                kind: "action::set",
+                projectName: response.projectName,
+                typeAcquisition: response.typeAcquisition,
+                compilerOptions: response.compilerOptions,
+                typings: emptyArray,
+                unresolvedImports: response.unresolvedImports,
+            });
+
+            host.checkTimeoutQueueLengthAndRun(2);
+            assert.isUndefined(request);
+        });
+
         it("ignores files excluded by the default type list", () => {
             const file1 = {
                 path: "/a/b/f1.js",
diff --git a/tests/baselines/reference/api/tsserverlibrary.d.ts b/tests/baselines/reference/api/tsserverlibrary.d.ts
index 0120e49f0a..d830655998 100644
--- a/tests/baselines/reference/api/tsserverlibrary.d.ts
+++ b/tests/baselines/reference/api/tsserverlibrary.d.ts
@@ -8497,7 +8497,7 @@ declare namespace ts.server {
         private readonly throttledOperations;
         private readonly hostConfiguration;
         private safelist;
-        private legacySafelist;
+        private readonly legacySafelist;
         private pendingProjectUpdates;
         readonly currentDirectory: NormalizedPath;
         readonly toCanonicalFileName: (f: string) => string;